DOE/ET/12099-3
( D E850065 84)
RESOURCE ASSESSMENT FOR GEOTHERMAL DIRECT
USE APPLICATIONS
BY
Christine Beer
William F. Hederman, Jr
Max R. Dolenc
David W. Allman
April 1984
Work Performed Under Contract Nos. AC07-801D12099
AC07-761C01570
ICF Incorporated
Washington, D.C.
and
EG&G Idaho, Inc.
Idaho Falls, Idaho
Technical Information Center
Office of Scientific and Technical Information
United States Department of Energy
DISCLAIMER
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The views and opinions of authors expressed herein do not necessarily state or
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DOE/ET/12099-3
(DE85006584)
Distribution Category UC-66g
RESOURCE ASSESSMENT FOR
GEOTHERMAL DIRECT USE APPLICATIONS
C h r i s t i ne Beer
W i l l i a m F. Hederrnan, Jr.
ICF I n c o r p o r a t e d
1850 K S t r e e t , N.W., S u i t e 950
Washington, D. C. 20006
Max R. Dolenc
D a v i d W. Allman
E d i t e d by
Ben C. L u n i s
EG&G I d a h o , i n c .
Box 1625
Idaho Falls, I D 83415
A p r i l , 1984
Prepared f o r t h e
Idaho Operations O f f i c e
U. S. Department o f Energy
D i v i s i o n o f Geothermal and Hydropower Techno i g i e s
Washington, DC 20585
Under DOE-ID C o n t r a c t Numbers
DE-AC07-80ID12099 and DE-AC07-76ID01570
ABSTRACT
T h i s r e p o r t d i scusses t h e t o p i c "geothermal r e s o u r c e assessment" and
i t s i m p o r t a n c e t o laymen and i n v e s t o r s f o r f i n d i n g geothermal r e s o u r c e s f o r
direct-use applications.
These a r e a p p l i c a t i o n s where t h e h e a t f r o m
l o w e r - t e m p e r a t u r e geothermal f l u i d s , 120-ZOOOF, a r e used d i r e c t l y r a t h e r
than f o r generating e l e c t r i c i t y .
The t e m p e r a t u r e s r e q u i r e d f o r v a r i o u s
a p p l i c a t i o n s a r e l i s t e d and t h e v a r i o u s t y p e s o f geothermal r e s o u r c e s a r e
described.
Sources o f e x i s t i n g r e s o u r c e d a t a a r e i n d i c a t e d , and t h e t y p e s
and s u i t a b i l i t y o f t e s t s t o d e v e l o p more d a t a a r e d e s c r i b e d .
Potential
development problems a r e i n d i c a t e d and guidance i s g i v e n on how t o decrease
t e c h n i c a l and f i n a n c i a l r i s k and how t o use t e c h n i c a l c o n s u l t a n t s
effectively.
The o b j e c t i v e s o f t h i s r e p o r t a r e t o p r o v i d e :
(1) an
i n t r o d u c t i o n l o w - t e m p e r a t u r e geothermal r e s o u r c e assessment; (2) e x p e r i e n c e
f r o m a s e r i e s o f r e c e n t d i r e c t - u s e p r o j e c t s ; and ( 3 ) r e f e r e n c e s t o
additional information.
Companion r e p o r t s d e s c r i b e t h e phases o f p r o j e c t
development w h i c h follow a p o s i t i v e r e s o u r c e assessment (DOE/ET/12099-4)
and an economic a n a l y s i s o f a few s e l e c t e d p r o j e c t s (DOE/ET/12099-5).
E x p e r i e n c e f o r t h i s r e p o r t was o b t a i n e d p r i m a r i l y f r o m 23 Department
o f Energy (DOE) sponsored Program O p p o r t u n i t y N o t i c e (PON) p r o j e c t s .
The
g o a l o f each DOE p r o j e c t was t o b u i l d and m o n i t o r t h e i n i t i a l o p e r a t i o n o f
a d i r e c t use geothermal system and t o make t h i s i n f o r m a t i o n a v a i l a b l e t o
t h e general p u b l i c .
About t h r e e - q u a r t e r s o f t h e s e p r o j e c t s a r e o p e r a t i n g .
Most o f t h e p r o j e c t s w h i c h were n o t completed d i d n o t l o c a t e an adequate
resource w i t h t h e f i r s t w e l l d r i l l e d .
ii
ACKNOWLEDGMENTS
The a u t h o r s g r a t e f u l l y acknowledge t h e c o n t r i b u t i o n s o f F r a n k C h i l d s
(EG&G I d a h o ) , Mike Tucker and E r i c P e t e r s o n (DOE), and t h e p r o j e c t s t a f f
p e r s o n n e l who were i n t e r v i e w e d .
iii
CONTENTS
..............................................................
INTRODUCTION ......................................................
BACKGROUND .......................................................
RESOURCE ASSESSMENT OVERVIEW .....................................
RESOURCE APPLICATIONS ............................................
4.1
General ....................................................
4.2
Commercial and Residential Space Conditioning ..............
4.3
Agriculture and Aquaculture Applications ...................
4.4
Industrial Processing Applications .........................
ii
.............................................
5.1
General ....................................................
5.2
Geothermal Fluid Flow ......................................
5.3
Geothermal Fluid Quality ...................................
RESOURCE ASSESSMENTS .............................................
General ....................................................
6.1
Legal Considerations .......................................
6.2
Permitting .................................................
6.3
Preliminary Geotechnical Assessment ........................
6.4
Conceptual Model Development ...............................
6.5
Exploration ................................................
6.6
Exploratory Well Drilling ..................................
6.7
Reservoir Testing ..........................................
6.8
PROJECT CONSIDERATIONS AND RISKS .................................
11
ABSTRACT
1.
2.
3.
4.
5.
6.
7.
RESOURCE EVALUATIONS
9.
3
4
6
6
6
8
8
11
11
11
17
17
17
19
20
21
21
26
27
29
General ....................................................
Resource Development Considerations and Risks . . . . . . . . . . . . . .
29
29
. . .......................... ..... .........
8.1
General ....................................................
8.2
Initial PON Project Interest ...............................
8.3
PON Project Resource Characteristics .......................
Cost Information ...........................................
8.4
CONCLUSIONS AND RECOMMENDATIONS ..................................
Conclusions ................................................
9.1
9.2
Recommendations ............................................
31
7.1
7.2
8.
1
PON PROJECTS EXPERIENCE
iv
31
34
34
40
42
42
43
10 . REFERENCES
.......................................................
APPENDIX..A Overview of Geothermal Resource Types .....................
44
A-1
FIGURES
1.
2.
.................
7
Temperatures required for various direct geothermal
applications .....................................................
10
Space heating and cooling with .geothermal fluids
3.
Known and potential hydrothermal resources
12
4.
Resource assessment decision tree
.......................
................................
18
5.
Recommended order of exploration surveys
25
6.
Outcomes of resource assessments
.........................
.................................
28
TABLES
1.
2.
Chemical constituents i n geothermal fluidsexploration uses and problems ....................................
14
Evaluation of application o f exploration/
assessment techniques for two regions ............................
22
...................................
23
...............................
32
3.
Cost of exploration activities
4.
Geothermal direct/use PON projects
5.
Reasons for PON projects interest i n resource development
6.
Expected v s . actual resource characteristics .....................
V
........
35
36
RESOURCE ASSESSMENT FOR
GEOTHERMAL DIRECT-USE APPLICATIONS
1.
INTRODUCTION
This report discusses the topic "geothermal resource assessment" and
its importance to laymen and investors for finding geothermal resources for
direct-use applications. These are applications where the heat from
lower-temperature geothermal fluids, 120-ZOOOF, are used directly rather
than for generating electricity. The temperatures required for various
applications are listed and the various types of geothermal resources are
described. Sources of existing resource data are indicated, and the types
and suitability of tests to develop more data are described. Potential
development problems are indicated and guidance is given on how to decrease
technical and financial risk and how to use technical consultants
effectively. The objectives of this report are to provide: (1) an
introduction 1 ow-temperature geothermal resource assessment; ( 2 ) experience
from a series of recent direct-use projects; and (3) references t o
additional information. Companion reports describe the phases of project
development which follow a positive resource assessment (DOE/ET/12099-4)
and an economic analysis of a few selected projects (DOE/ET/12099-5).
This report describes the general procedures for geothermal resource
assessment plus a menu of specific activities which may be used. It notes
t h e dependence of t h e a c t i v i t i e s upon t h e s p e c i f i c c o n d i t i o n s a t each
potential resource site. Technical terms are defined and presented so that
they can be understood by the layman with little familiarity with
geothermal energy. With this in mind, the report tries t o keep the
relative importance of activities i n perspective and presents them i n a
logical or chronological manner. The need to match the potential resource
characteristics with the requirements of prospective applications is
noted. The app,roximate cost of resource assessment techniques and the
effects o f other factors on project payback are indicated.
1
,
Experience f o r t h i s r e p o r t was o b t a i n e d p r i m a r i l y from 23 Department
of Energy (DOE) sponsored Program Opportunity Notice (PON) p r o j e c t s .
The
goal of each DOE p r o j e c t was t o b u i l d and monitor the i n i t i a l o p e r a t i o n of
a d i r e c t use geothermal system and t o make t h i s information a v a i l a b l e t o
the general p u b l i c . About t h r e e - q u a r t e r s of t h e s e p r o j e c t s a r e o p e r a t i n g .
Most o f the p r o j e c t s which were not completed d i d n o t l o c a t e an adequate
r e s o u r c e w i t h t h e f i r s t well d r i l l e d .
T h i s r e p o r t i s n o t a r r a n g e d t o provide d e t a i l e d h i s t o r y o f each of the
PON p r o j e c t s b u t r a t h e r t o a d d r e s s t h e major a c t i v i t i e s and concerns i n the
e v a l u a t i o n of a p r o j e c t , such a s d e f i n i n g the needs w i t h r e s p e c t t o the
p r o c e s s being c o n s i d e r e d , the l e g a l a s p e c t s , p e r m i t t i n g and e x p l o r a t i o n , a s
well a s the v a r i o u s c o n s i d e r a t i o n s and r i s k s a t each p o i n t .
Development, which would f o l l o w a p o s i t i v e r e s o u r c e assessment, i s
d i s c u s s e d i n more d e t a i l i n a companion r e p o r t . 1
2
2.
BACKGROUND
The r i s e i n i m p o r t e d o i l and n a t u r a l gas p r i c e s and t h e l i k e l i h o o d o f
f u r t h e r e v e n t u a l i n c r e a s e s , e s p e c i a l l y f o r n a t u r a l gas',
t h e d e s i r a b i l i t y o f d e v e l o p i n g d o m e s t i c energy r e s o u r c e s .
have enhanced
Declining
d o m e s t i c p r o d u c t i o n o f c r u d e o i l and e n v i r o n m e n t a l problems l i m i t i n g t h e
expanded use o f o t h e r c o n v e n t i o n a l energy r e s o u r c e s have a l s o s t i m u l a t e d
t h e search f o r v i a b l e a l t e r n a t i v e s .
One o f t h e most p r o m i s i n g o f t h e
a l t e r n a t e energy t e c h n o l o g i e s has p r o v e d t o be t h e u t i l i z a t i o n o f o u r
n a t i o n ' s geothermal r e s o u r c e s .
These geothermal r e s o u r c e s r e p r e s e n t a v a s t energy a s s e t t h a t i s f r e e
o f foreign control o r interference.
If a l l o f t h e geothermal r e s o u r c e s
i d e n t i f i e d i n t h e U n i t e d S t a t e s G e o l o g i c a l S u r v e y ' s C i r c u l a r 790
3
were
u t i l i z e d , t h e t o t a l energy a v a i l a b l e a t t h e w e l l h e a d f r o m r e s o u r c e s above
90°C w o u l d be e q u i v a l e n t t o 450 b i l l i o n b a r r e l s o f o i l - - m o r e
t h a n 16 t i m e s
t h e known o i l r e s e r v e s o f t h e e n t i r e n a t i o n .
U n l i k e development o f some a l t e r n a t e energy r e s o u r c e s , t h e use o f
geothermal energy does n o t depend on new e n g i n e e r i n g o r s c i e n t i f i c
advances, but r e q u i r e s o n l y t h e m i n o r a d a p t a t i o n o f e x i s t i n g t e c h n o l o g y ,
t h e e n v i r o n m e n t a l consequences o f w h i c h a r e r e l a t i v e l y b e n i g n .
A p p l i c a t i o n s o r uses o f geothermal energy a r e commonly d i v i d e d i n t o
two categories: (a) direct use o f the energy for purposes o f agriculture,
a q u a c u l t u r e , w a t e r and space h e a t i n g , and i n d u s t r i a l p r o c e s s i n g , and (b)
i n d i r e c t use f o r g e n e r a t i n g e l e c t r i c power.
P r o j e c t s t o w h i c h geothermal
energy can be d i r e c t l y a p p l i e d u s u a l l y r e q u i r e w e l l h e a d t e m p e r a t u r e s
between 120-200°F.
Heat pumps can a l s o b e used w i t h l o w t e m p e r a t u r e
geothermal r e s o u r c e s t o augment t h e l o w t e m p e r a t u r e uses.
E l e c t r i c power
g e n e r a t i o n u s u a l l y r e q u i r e s much h i g h e r r e s o u r c e t e m p e r a t u r e s .
With a
b i n a r y w e l l h e a d e l e c t r i c g e n e r a t o r , t e m p e r a t u r e s as l o w as 190OF have been
used, b u t economics improve w i t h i n c r e a s i n g t e m p e r a t u r e (steam-dominated
r e s e r v o i r s i n t h e 500-70O0F range a r e p r e f e r r e d b u t r a r e l y f o u n d ) .
3
3.
RESOURCE ASSESSMENT OVERVIEW
Assessment of a geothermal resource requires a careful step-by-step
procedure in which low cost activities are used in the first steps to
eliminate projects that have an unacceptable risk. Confirmation of
geothermal reservoirs by drilling is costly, and the risk of drilling an
unacceptable well i s significant. Therefore, the prospective developer or
user should follow an orderly procedure to minimize the risks.
The first step in the process is resource identification. potential
direct-heat users cannot, in general, afford to do the regional geologic
work or geothermal data compilation that is needed to identify those sites
where reservoir confirmation studies are most likely to succeed, but they
can obtain valuable information from the United States Geological Survey
(USGS) and from the individual states geological departments. State
universities may also be consulted. These organizations have inventoried
various surface manifestations such as hot springs and fumaroles,a and
they have records on thermal wells. In some areas, it is possible to
obtain an estimate of the expected temperatures, and this information can
be used in feasibility studies aimed at the prospective application.
The developer should assure himself that there is a reasonable
probability that a resource exists in an area where his intended process
can be located. He should also assure himself that there is a reasonable
probability that the temperature will be adequate for the intended
application. Generally speaking, this initial screening can be
accomplished by personnel unfamiliar with geothermal utilization using the
aforementioned sources of information.
If the prcject appears feasible, the developer should next acquire the
services of a geological consultant for the site specific geological
analysis. A qualified consultant can give valuable assistance for
preparation or an update of an economic and engineering analysis by
a.
Fumarole--Hole, vent, spring or geyser which emits considerable
quantities o f gases, vapor or steam.
4
p r o v i d i n g e x p e r t o p i n i o n on p r o b a b l e w e l l d e p t h , t e m p e r a t u r e s and f l o w
rates.
The c o n s u l t a n t s h o u l d a l s o p r e p a r e a r e s o u r c e development p l a n , and
he can e i t h e r a s s i s t i n an e n v i r o n m e n t a l assessment o r recommend someone
e l s e who can h e l p .
The p r e c e d i n g d i s c u s s i o n i s meant t o emphasize t h e f a c t t h a t t h e
development o f geothermal r e s o u r c e s has an i n h e r e n t r i s k , b u t t h i s r i s k can
be reduced i f a good j o b i s done i n t h e work t h a t i s p e r f o r m e d p r i o r t o
well d r i l l i n g .
Maximum r e t u r n on i n v e s t m e n t r e q u i r e s t h e r e j e c t i o n o f a l l
d r i l l i n g s i t e s which do n o t appear t o be v e r y p r o m i s i n g f r o m t h e c o m p i l e d
p r e d r i l l i n g data.
Economic, e n g i n e e r i n g and e n v i r o n m e n t a l l i m i t a t i o n s
s h o u l d be r e v i e w e d a t each s t a g e o f t h e p r o j e c t t o p r e v e n t a d d i t i o n a l
i n v e s t m e n t i n an area w h i c h cannot be p r o f i t a b l y developed.
5
4.
RESOURCE APPLICATIONS
4.1 General
Numerous direct use app ications o f geothermal fluids exist, with the
three primary use categories being;
(1) Commercial and res dential space conditioning
(2)
Agricultural and aquaculture
(3)
In ustrial processing.
This section provides a brief overview of these uses, the applicable
geothermal f uid temperature requirements, and comments on PON project
activities.
4.2
Commercial Residential Space Conditioning
Geothermal fluids can be used for heating and cooling residential and
commercial buildings. Figure 1 compares different types of heating and
cooling applications with geothermal fluid temperatures. Cooling of
buildings generally require geothermal fluid temperatures above Z O O O F , but
the best economics occur when the refrigeration systems are driven by
geothermal steam. Depending upon specific needs and geothermal fluid
characteristics, space conditioning can be provided for single or multiple
building applications utilizing a variety of systems. Nineteen of the
twenty-three PON projects were developed to verify the technical
feasibility and economic worth of space and/or hot water heating
applications. Several projects have been developed into operating district
heating systems in Boise, Idaho; Susanville, California; Philip, South
Dakota; Pagosa Springs, Colorado, and Elko, Nevada. A district heating
system is under development at Klamath Falls, Oregon under the DOE PON
program. In addition, from private development, there are presently more
than 500 homes heated geothermally in Klamath Falls, where most of these
homes uti-lize a downhole heat exchanger in a single well to heat a single
6
7
212OF
100°C
loooFSOo F
. 50°F
32OF O°C
5
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5
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(d
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residence. Currently, a typical residential heating system in Klamath
Falls uses a 10-in. diameter, 300-ft deep well with two downhole heat
exchangers. One is for the space heating system and one is for the
domestic hot water system. The heat exchangers are placed in wells with
temperatures ranging from 140 to 205OF (60 to 96OC). City water is
recirculated in the space heating loop through a heat exchanger in the
home's forced-air system, baseboard convectors, or radiant panels. 4
4 . 3 Aqriculture and Aquaculture Applications
Agricultural and aquacultural uses of geothermal energy for heating
include: space heating for greenhouses and animal husbandry, air heating
for crop drying, and warm water supplies for fish farming. Industrial
applications include food preparation processes, such as pasteurization of
milk, beer, and other consumable liquids, as well as dehydration of
vegetables; pulp, paper, and wood processing; and heating f o r kiln drying
of lumber. A great potential for use of geothermal fluids exists because
there is an abundant supply of geothermal resources that can meet the
80 to 18OOF temperature requirements for most of the
agriculture/aquaculture uses three PON projects applying to this category
were successfully demonstrated: (a) geothermal energy is used to heat a
six-acre greenhouse near Salt Lake City, Utah, (b) Diamond Ring Ranch near
Midland, South Dakota, utilizes geothermal energy for grain drying and
space heating, and (c) Aquafarms International, in the Coachella Valley of
California, has exploited a low temperature geothermal resource [86OF
(3OOC) wellhead temperature] i n a successful prawn farming project.
Geothermal fluid is used to maintain year-round desired temperatures i n
50 acres of ponds.
4.4
Industrial Processing Applications
Industrial processing applications may be more financially attractive
than seasonal space heating applications, since they usually operate
continuously near peak load and have the potential to generate more revenue
than a seasonal system of the same capital cost. However, such
applications often require greater resource flow rates and higher
a
temperatures than other direct-heat a p p l i c a t i o n s .
Temperature r e q u i r e m e n t s
f o r i n d u s t r i a l a p p l i c a t i o n s range f r o m 60 t o 3OOOF (10 t o 15OOC).
Figure 2
l i s t s a v a r i e t y o f i n d u s t r i a l processes and t h e i r r e s p e c t i v e p r o c e s s
temperature requirements.
Mixed r e s u l t s have been o b t a i n e d f o r i n d u s t r i a l
a p p l i c a t i o n s u s i n g geothermal f l u i d s as evidenced b y t h e i n a b i l i t y t o f i n d
adequate geothermal r e s o u r c e s f o r t h e t h r e e PON p r o j e c t s (Ore-Ida Foods,
O n t a r i o , Oregon; H o l l y Sugar/TRW,
Brawley, C a l i f o r n i a ; and Madison County,
Rexburg, I d a h o ) a p p l i c a b l e t o t h i s c a t e g o r y .
Other i n d u s t r i a l p r o j e c t s
have p r o v e n t o be s u c c e s s f u l , two o f w h i c h a r e t h e Medo-Bel Creamery ( m i l k
p a s t e u r i z a t i o n ) i n Klamath F a l l s , Oregon; and Geothermal Food Processors
( v e g e t a b l e d e h y d r a t i o n ) a t Brady H o t S p r i n g s , Nevada.
9
X'
IbC
50. F
L
1490c
100-
150.
1
I
200.
250-
I
I
300°F
I
Malt beveragas
Distilled liquor
Scalding
Soft drinks
Biogas processas
c
Gypsum d r y i n g
4
Alumina
cc
Aggregate d r y i n g
Cement drying
Rubber vulcanization
Sty rene
Autoclaving and cleanup
Pharmaceutical
Acrylic
Kaolin d r y i n g
Organic chemicals
Lumber
Textile mill
Rayon /acetate
Coal d r y i n g
Pulp and paper
Concrete block c u r i n g
Synthetic r u b b e r
Metal p a r t s washing
Leather
Furniture
Beet sugar evaporation
Cane sugar evaporation
Beet sugar pulp d r y i n g
Blanching and cooking
F r u i t and vegetable d r y i n g
Whey condensing
Milk evaporation
Beet sugar extraction
Carcass wash and cleanup
Pasteurization
Mushroom c u l t u r e
Food processing
Pickling
Greenhou sing
Aquaculture
Soil warming
I
50-F
.:, c
Source:
Oregon:
Flaure 2.
I
100-
1
150.
1
200-
I
250.
i
:g?:F
A Guide to Geothermal Energy Development, 2. &.
Temperatures Required f o r Various Direct .Geothermal Applications
10
5.
RESOURCE EVALUATIONS
5.1 General
Geothermal r e s o u r c e s occur i n a v a r i e t y of g e o l o g i c environments, and
a r e known t o e x i s t through v e r i f i c a t i o n and by i n f e r e n c e a t many l o c a t i o n s
throughout t h e United S t a t e s and the world.
Appendix A p r o v i d e s an
overview of the d i f f e r e n t t y p e s of r e s o u r c e s and t h e i r PON p r o j e c t
Figure 3 i s provided t o give an i n d i c a t i o n of t h e magnitude
of the geothermal p o t e n t i a l i n the United S t a t e s . 5
relationship.
Numerous items need t o be c o n s i d e r e d i n t h e development of t h e s e
geothermal r e s o u r c e s , which i n v o l v e e x p l o r a t i o n , c o n f i r m a t i o n , d r i l l i n g ,
and t e s t i n g programs t h a t draws upon the s k i l l s of g e o l o g i s t s , geochemists,
g e o p h y s i c i s t s , h y d r o l o g i s t s , r e s e r v o i r e n g i n e e r s and o t h e r s . T h i s s e c t i o n
p r o v i d e s information r e l a t i v e t o r e s o u r c e e v a l u a t i o n s , i n c l u d i n g flow and
water q u a l i t y r i s k s , r e s o u r c e i n v e s t i g a t i o n s , r e s o u r c e assessment and
e x p l o r a t i o n , and d r i l l i n g and t e s t i n g .
P r a c t i c a l a p p l i c a t i o n s of t h e s e
a c t i v i t i e s a r e provided through PON p r o j e c t a c t i v i t i e s , and t h e e x p e r i e n c e
gained t h e r e b y i s a l s o i n c l u d e d .
5.2
Geothermal F l u i d Flow
Geothermal f l u i d flow, u s u a l l y measured i n g a l l o n s p e r minute (gpm),
can be a s important a r e s o u r c e requirement a s t e m p e r a t u r e . T h e r a t e a t
w h i c h thermal energy can be e x t r a c t e d from a geothermal r e s o u r c e depends
not only on t h e temperature of the f l u i d , b u t a l s o on i t s q u a n t i t y . ( I t i s
p r o p o r t i o n a l t o the product o f the flow r a t e and t h e number o f d e g r e e s of
temperature removed from the f l u i d . ) I n s u f f i c i e n t flow, t h e r e f o r e , can
make an o t h e r w i s e economical and d e s i r a b l e geothermal p r o j e c t i n f e a s i b l e .
5 . 3 Geothermal F l u i d Q u a l i t y
Geothermal- f l u i d s c o n t a i n chemicals o r d i s s o l v e d s o l i d s w h i c h can
g r e a t l y a f f e c t p r o j e c t economics.
G e n e r a l l y t h e s o l i d s c o n t e n t of
geothermal f l u i d s i n c r e a s e w i t h temperature b u t there can be a wide
11
Figure 3. Known and Potential Hydrothermal Resources
A developer should
v a r i a t i o n i n s o l i d s c o n t e n t a t any t e m p e r a t u r e .
i n v e s t i g a t e as soon as p o s s i b l e t h e expected s o l i d s c o n t e n t o f f l u i d s i n an
area because o f t h e i r p o t e n t i a l adverse e f f e c t s .
Five considerations are
as f o l l o w s :
1.
System d e s i g n and p r o j e c t economics w i l l be impacted i f f l u i d
t r e a t m e n t is r e q u i r e d .
2.
Water q u a l i t y may l i m i t f l u i d d i s p o s a l a l t e r n a t i v e s , e s p e c i a l l y
i n l i g h t o f m e e t i n g EPA and s t a t e e n v i r o n m e n t a l s t a n d a r d s .
3.
C o r r o s i v e f l u i d o r f l u i d t h a t causes s c a l i n g i n f l u e n c e s m a t e r i a l s
s e l e c t i o n and d e s i g n o f t h e system, as w e l l as p r o j e c t economics.
4.
F l u i d c o m p o s i t i o n can p r o v i d e v a l u a b l e i n f o r m a t i o n t h a t u s u a l l y
h e l p s d e f i n e t h e ground-water f l o w system(s) i n t h e v i c i n i t y o f
t h e geothermal r e s o u r c e .
5.
Geothermometry can p r o v i d e e s t i m a t e s o f t h e maximum p o s s i b l e
r e s o u r c e t e m p e r a t u r e t h a t can be expected.
Techniques f o r d e a l i n g w i t h c o r r o s i v e and/or s c a l i n g geothermal f l u i d s
a r e s t i l l b e i n g developed.
F l u i d s w i t h t h e h i g h e s t temperatures are
u s u a l l y t h e most d e s i r a b l e f o r p r o j e c t a p p l i c a t i o n s , y e t as t e m p e r a t u r e
i n c r e a s e s t h e r e i s t y p i c a l l y an i n c r e a s e i n t o t a l d i s s o l v e d s o l i d s (TDS)
and o t h e r u n d e s i r a b l e c o n s t i t u e n t s and gases.
b a r r i e r s t o resource u t i l i z a t i o n .
P o o r q u a l i t y w a t e r can pose
T a b l e 1 l i s t s some m a j o r c o n s t i t u e n t s
t h a t a r e o f use i n d e f i n i n g t h e r e s o u r c e and some o f t h e problems t h e s e
c o n s t i t u e n t s may p r e s e n t .
F o r f u r t h e r i n f o r m a t i o n on t h e s i g n i f i c a n c e o f
i n d i v i d u a l chemical c o n s t i t u e n t s , t h e r e f e r e n c e d Geothermal Resources
C o u n c i l S p e c i a l R e p o r t Number 7 p r o v i d e s a d d i t i o n a l d a t a .
The d e t e r m i n a t i o n o f c o n c e n t r a t i o n s o f p a r t i c u l a r d i s s o l v e d s p e c i e s i s
necessary i n t h e r e s o u r c e assessment process.
S i g n i f i c a n t concentrations
o f s u l f a t e s , c h l o r i d e s , and o t h e r chemical s p e c i e s can r e s u l t i n a h i g h l y
c o r r o s i v e f l u i d f o r w h i c h s p e c i a l and perhaps c o s t l y p i p i n g systems m i g h t
13
TABLE 1.
CHEMICAL CONSTITUENTS I N GEOTHERMAL FLUIDS--EXPLORATION LOSSES
AND PROBLEMS
Uses
Constituent/Parameter
H I o n C o n c e n t r a t i o n (pH)
d e
REDOX P o t e n t i a1 (Eh)
d
Speci f ic Conductance
b d e
T o t a l D i s s o l v e d S o l i d s (TDS)
b d e f
Cal c i um (Ca++)
a b e
Magnesium (Mg++)
a b e
Sodium (Na')
a b
Potassium <K+)
a b
Chloride (Cl-)
b d f
S u l f a t e (SO4)
b c f
B i c a r b o n a t e (HCO,) "
b d e
Carbonate (Cog)
b d e
F1 u o r i d e (F-)
b f
L i t h i um (L1')
b
Boron (B+++)
b f
A r s e n i c (As+)
b c f
M e r c u r y (Hg++)
b c
Oxygen 18 (0l8)
a b
D e u t e r i urn (D)
b
H e l i u m (He)
b c
Radon (Rn)
b c
Tritium
(H 3 )
b
S i l i c a (SiO?)
a b e
14
TABLE 1.
(continued)
Constituent/Parameter
Uses
Hydrogen sulfide (HzS)
d f
Carbon dioxide (COz)
d
A.mrnoni a ( NH3)
d
Sul fides
e
Oxides
e
Gross
u
and 6 Radioactivity
f
a. Geothermometry.
b.
Ground-water flow system( s)/mi xi ng .
c. Exploration using soil gases/particulates if constituents exist i n the
geothermal f 1 uid.
d.
Corrosion potential.
e.
Scaling potential.
f.
Common environmental problems.
15
be necessary.
S i m i l a r d i f f i c u l t i e s a r i s e w i t h t h e presence o f s i l i c a t e s ,
carbonates, s u l f i d e s , and o x i d e s w h i c h can cause s c a l i n g .
Exposing t h e
geothermal f l u i d t o oxygen i n t h e a i r w i l l i n c r e a s e c o r r o s i o n a c t i v i t y .
F l a s h i n g t h e geothermal f l u i d may p e r m i t d i s s o l v e d C02 and o t h e r
d i s s o l v e d gases t o come o u t o f s o l u t i o n and cause t h e p r e c i p i t a t i o n o f
calcium carbonate o r o t h e r minerals.
E x c e s s i v e c o n c e n t r a t i o n s o f boron,
a r s e n i c , l e a d , o r radium-226 w i l l cause e n v i r o n m e n t a l problems, t h u s
n e c e s s i t a t i n g i n j e c t i o n and/or chemical t r e a t m e n t , w h i c h w i l l i n c r e a s e
system c o s t s .
T h e r e f o r e , i n a d d i t i o n t o t e m p e r a t u r e and f l o w
c h a r a c t e r i z a t i o n , chemical a n a l y s i s and c o r r o s i o n coupon t e s t s w i t h
candidate materials o f construction are generally required i n the
development o f a new r e s o u r c e .
16
6.
RESOURCE ASSESSMENTS
6.1
General
A l o g i c a l approach t o r e s o u r c e assessment ( F i g u r e 4 )
f o r t h e p o t e n t i a l developer o r i n v e s t o r .
7
i s provided
W i t h t h i s approach, i t i s assumed
t h a t t h e d e v e l o p e r / i n v e s t o r i s aware o f a t h e r m a l anomaly w i t h i n a
r e a s o n a b l e p i p e l i n e d i s t a n c e f o r a p p l i c a t i o n i n one o r more i n t e n d e d end
uses o r m a r k e t s .
The m a j o r u n c e r t a i n t y a t t h i s s t a g e i s , "can t h e
p o t e n t i a l l y a v a i l a b l e geothermal f l u i d s be employed i n an economical
manner?"
I f r e p l a c i n g a c u r r e n t f u e l source i s t h e i s s u e , t h e c o s t o f
r e t r o f i t and t h e s e l l i n g p r i c e o f t h e geothermal f l u i d v e r s u s t h e p r e s e n t
and p r o j e c t e d c o s t o f t h e c o m p e t i t i v e f u e l must a l s o be c o n s i d e r e d .
These
a r e g e n e r a l i n v e s t m e n t d e c i s i o n s t y p i c a l o f most a p p l i c a t i o n s a s s o c i a t e d
w i t h energy o r f u e l r e q u i r e m e n t s .
The p o t e n t i a l d e v e l o p e r / i n v e s t o r a t t h i s s t a g e has t h e problem o f how
t o assess t h e t h e r m a l anomaly w i t h minimum i n v e s t m e n t .
I t i s t h e goal of
t h i s s e c t i o n t o p r o v i d e i n f o r m a t i o n a b o u t t h e key t a s k s i n v o l v e d i n t h e
d e c i s i o n making process.
6.2
Legal C o n s i d e r a t i o n s
One o f t h e f i r s t s t e p s i n p r o c e e d i n g w i t h an assessment o f t h e
r e s o u r c e i s t o d e t e r m i n e t h e l e g a l d e f i n i t i o n of geothermal f l u i d s i n t h e
s t a t e i n w h i c h t h e development i s t o o c c u r .
geothermal energy as a " m i n e r a l resource,"
resource."
Some s t a t e s c o n s i d e r
o t h e r s as a "geothermal
A n o t h e r c o n s i d e r a t i o n t h a t d i f f e r s between s t a t e s i s t h a t t h e
t e m p e r a t u r e o f t h e f l u i d o r t h e use o f t h e f l u i d d e t e r m i n e s t h e p r o j e c t ' s
legal status.
Coupled t o t h e s e a r e a number o f m a j o r c o n s t r a i n t s t h a t
i n c l u d e p e r m i t t i n g r e g u l a t i o n s , t a x t r e a t m e n t , and o t h e r f a c t o r s which may
a f f e c t t h e p r o j e c t economics.
17
FEASIBILITY ANALYSIS'
/-
\
\
H 4 e l i m i n a r y resource
estimate, conceptual
design, and market and
\ economic analysis.
<
\
RESOURCE ASSESSMENT
\
/
,'
y
' ,
/
Begin exploration
process
>and hydrology literature
+
~
Regional field
sampling and mapping
Terminate project
t
Target resource
via conceptual model
Geochemical
studies
Thermal gradient
studies (May
require permitting)
Hydrologic
studies
Upgrade target and
conceptual model
Legend
0 Decision point
1-1
Operation to produce
Detailed
geologic
mapping
1
<
Target and model
Accomplish
confidence vs
Poor
geophysical
m
cost of additional
survey
data and knowledge-gained
(requires permitting)
Figure 4. Resource Assessment Decision Tree
18
The land and resource ownership needs to be established after
determining the legal definition of the geothermal resource. Information
on land ownership may be obtained from sources such as:
1.
Bureau of Land Management (federal lands)
2.
State land and water rights offices (state and private lands)
3
Municipal offices (private lands)
4
County offices (private lands).
6.3 Permitting
The procedure for obtaining lease permits varies according to state
laws when the land is private or state owned, to federal laws when the land
is federally owned, and to other regulations (and the agreement between the
owner and the developer) if the land is privately owned. When mineral
rights have been severed from the surface ownership, subsurface rights must
be obtained in addition to surface rights. If field exploration is
conducted before obtaining a lease, it may increase the cost of the lease,
especially as resource discovery becomes apparent. If negotiations for the
desired leases/rights do not result in an economically satisfactory
agreement, the only recourse is to terminate the proposed project at this
stage. The exploration process may begin if negotiations are successful.
Requirements for permitting are usually associated with considerations
o f leasing and land ownership. This activity is a function of the
regulatory agency having jurisdiction (i.e., state or federal). State
permit requirements vary; therefore, this discussion will center on
obtaining federal permits. State agencies should be individually consulted
for information pertaining to specific states.8
"Casual use activities'' during pre-lease exploration require no
permits on federal lands. Casual use involves activities that (a) do not
appreciably disturb the land, improvements, or other resources, (b) do not
require heavy equipment or explosives, and (c) confine vehicles to
19
If temperature gradient holes (shallower than
establlshed roads.'
500 ft) are drilled, geophysical surveys are conducted, new roads are
necessary, or other intensive exploration is carried out, a "Notice of
Intent and Permit to Conduct Exploration Operations" must be filed with the
Minerals Management Service (MMS) of the Bureau of Land Management.
Beyond the above listed activities allowed on a pre-lease basis, all
future activities require permit approval by the MMS. All well drilling,
alterations, and abandonment methods, plus a detailed plan of operations)
are regulated and require approval. Appropriate state agencies are
consulted by MMS to insure compliance with state law on the federal
leaseholdings. Assurance of conducting all operations in a prudent manner
i s implicit in the carrying out of these regulations.
Depending on the specific locality, some counties require "land use"
approvals, particularly where affected by strict zoning laws. Similarly,
if wells o r operations are conducted within city limits, approvals are
necessary from city administrators. It is best for the developer to
consult appropriate state and federal officials before pursuing development
on a given property.
The next step in assessing a resource is to develop an exploration
target concept. This is best accomplished by a geoscientific
consultant(s).
(Consultants are discussed i n greater detail in
Reference 1.) The consultant will initiate the exploration process by
means of a literature search to obtain all existing hydrogeologic
information on the potential geothermal site. Before contracting with
geologists, geophysicists, and geochemists) the developer/investor may
decide to search federal, state, county, and municipal records, and if
available, local driller's logs for technical information and advice.
(Drillers logs are often on file with the state.)
The purpose of this early exploration stage literature search is to
aid in reducing the time and financial investment o f the developer.
20
I
D e s i r e d i n f o r m a t i o n would p e r t a i n t o t h e l o c a t i o n arrd d i s t r i b u t i o n o f
t h e r m a l and m i n e r a l s p r i n g s , warm w a t e r w e l l s , f a u l t s , and chemical
a n a l y s e s o f t h e r m a l and nonthermal w a t e r s .
The c o n s u l t a n t may use a
r e g i o n a l f i e l d sampling and mapping program t o o b t a i n such i n f o r m a t i o n i f
i t i s not available.
6.5
Conceptual Model Development
The c o n s u l t a n t w i l l h o p e f u l l y be a b l e t o f o r m u l a t e a c o n c e p t u a l model
o f t h e r e s o u r c e from t h e accumulated d a t a base t h a t w i l l p r o v i d e a g e n e r a l
i n d i c a t i o n o f t a r g e t depths, temperatures, and f l u i d c o m p o s i t i o n .
This i s
a d e c i s i o n p o i n t a s t o whether t o proceed, t e r m i n a t e t h e p r o j e c t , o r pursue
a more d e t a i l e d e x p l o r a t i o n program.
It i s a l s o a major technical data
i n p u t p o i n t w h i c h s h o u l d be used t o reassess t h e p r o j e c t economics.
6.6
Exploration
Given f a v o r a b l e c o n d i t i o n s , e s p e c i a l l y w i t h r e g a r d t o r e s o u r c e
t e m p e r a t u r e , depth, and p o t e n t i a l well y i e l d s , geothermal e x p l o r a t i o n can
begin.
Table 2 l i s t s t h e general a p p l i c a b i l i t y o f exploration/assessment
t e c h n i q u e s t o two g e o g r a p h i c a l r e g i o n s . lo There a r e t h r e e b a s i c
e x p l o r a t i o n techniques--geographical
, g e o p h y s i c a l , and geochemical--each o f
w h i c h w i l l be d i s c u s s e d below w i t h emphasis on p r o c e d u r a l methods and
t e c h n i c a l importance.
T a b l e 3 l i s t s approximate c o s t f i g u r e s f o r
exploration activities.
G e o l o g i c s i t e e v a l u a t i o n and a e r i a l reconnaissance a i d i n d e t e r m i n i n g
t h e p o s s i b l e s i z e and n a t u r e o f a h y d r o t h e r m a l system.
O f t e n much o f t h e
g e o l o g i c e x p l o r a t i o n p r o c e s s can be a v o i d e d by g a t h e r i n g and a n a l y z i n g
e x i s t i n g geological surveys which cover t h e s i t e o f t h e hydrothermal
system.
I f e x i s t i n g d a t a a r e u n a v a i l a b l e , c o n v e n t i o n a l f i e l d methods
s h o u l d b e used t o d e t e r m i n e t h e e x i s t e n c e o f t h o s e g e o l o g i c c o n d i t i o n s
w h i c h a r e u s u a l l y a s s o c i a t e d w i t h geothermal energy, e.g.,
21
young v o l c a n i c
TABLE 2.
EVALUATION OF APPLICATION
OF EXPLORATION/ASSESSMENT TECHNIQUES
FOR TWO REGIONS~
Legend:
Technique
B a s i n and Range
Wasatch
Front
Thermal method
1
1
Surface geological
mapping
2
2
Gravimetry
7
7
E l e c t r i c a l methods
4
4
Borehole logging
8
8
S e i srnic method
5
5
L i q u i d geochemistry
3
3
A i r photogeology
6
9
Age d a t i n g
9
6
Magnetics
10
10
Gas geocherni s t r y
13
13
Remote s e n s i n g
12
11
Thermal i n f r a r e d
11
12
Other
14
14
1
-
Most a p p l i c a b l e : 14 = L e a s t a p p l i c a b l e
B a s i n and Range i s t h e g e o l o g i c p r o v i n c e w h i c h c o v e r s Nevada,
w e s t e r n Utah, and s o u t h e a s t e r n and e a s t - c e n t r a l I d a h o .
The Wasatch F r o n t i s t h e e a s t e r n boundary o f t h e b a s i n and r a n g e .
I t i s t h e w e s t e r n f o o t o f t h e mountain range w h i c h r u n s
n o r t h - s o u t h t h r o u g h t h e m i d d l e o f n o r t h e r n Utah.
The B a s i n and Range and Wasatch F r o n t r e g i o n a r e t y p i c a l o f a
f r a c t u r e - c o n t r o l l e d d e e p - c i r c u l a t o r y systern.
a.
(After Dhillon e t al.,
1978.) 9
22
TABLE 3 .
COST OF EXPLORATION A C T I V I T I E S
~
Met hod
Time
Consulting Geologist
< Month
A i rphoto I n t e r p r e t a t i o n
< Month
Water A n a l y s i s
Month
Area
Expense
$200
$100
-
$400/day
Regional/Detai led
$5/m i 2
Reg i ona I/Deta i I ed
$200/sample
Regional/Detai led
S u r f a c e Geochemistry
Month
$30/sample
Detailed
V o l a t i l e Geochemistry
Month
$20/samp I e
Deta i l e d
> Month
$10
-
$lOO/ft
E Iec t romagne t I c Methods
Month
$200
-
$1,500/
ine m
Deta i l e d
Res i s t i v i t y
Month
$200
-
$1,500/
ine m
Deta i l e d
ine m
Reg iona I
Teriiperature Grad ient/Hea t Flow Boreho I es
Magnetics
Seismic
N
w
-
Regional/Detailed
Airborne
<Month
Ground
< Month
$200/1 i n e m i
Deta i l e d
Refraction
< Month
$5000/I i ne m I
Deta i l e d
Reflection
<Month
Micro-Ea r t h q u a kes
3 - 6 Months
$25/
$500
-
Gravity
Month
$30
Magne t o t c I Iu r i c s
Month
$1,200
Geophys i ca I Logg ing
<Week
$2,000
~~~~
$10,000/11ne
mi
Deta i l e d
$1,20O/day
Reg iona I / D e t a i l e d
$70/station
Reg iona I/Deta i Ied
-
2,000/1ine
mi
$20,00O/ho I e
Deta i l e d
Note:
C o s t s shown a r e approximate and w i l l v a r y a s a f u n c t i o n of many f a c t o r s i n c l u d i n g s u r v e y d e t a i l ,
l o c a t i o n , a c c e s s i b i l i t y , and weather.
The c o s t s f o r geothermal e x p l o r a t i o n i n c l u d e sample c o l l e c t i o n and
c hem ica I a na Iy s i s
.
Source:
Geothermal Resources Counci I S p e c i a l R e p o r t No. 7,
T e c h n i c a I Handbook, 1979, p. 2-14.
D i r e c t U t i I i z a t i o n o f Geothermal Energy:
A
formations, faults, tufa mounds,a hydrothermally altered rock,b hoi
springs, etc. Aerial and satellite photography can be extremely useful in
locating fault zones and hot spring deposits.
The characteristics of the exploration techniques in Figure 5 are
briefly addressed below. Resistivity surveys are concerned with the
subsurface distribution o f the apparent soil-water resistivity. Low
resistivity anomalies are normally associated with geothermal resources
because of the elevated ground-water temperature, degraded ground-water
quality, and hydrothermally altered rock. In the geochemical soil survey,
soil particulate and gas samples are collected and analyzed for
constituents such as mercury, radon, helium, and other inert gases commonly
associated with geothermal activity. Abnormally high concentrations of one
or more of these constituents can be expected i n a geothermal discharge
area. Thermal gradient holes can be used to delineate where elevated
subsurface temperatures can be attained with the least amount o f drilling.
(In some states, these wells may require permitting.) Gravity surveys are
used to delineate subsurface geologic structures based on rock density
differences. Seismic techniques use the different seismic velocity
transmitting characteristics of rocks to indicate geologic structures such
as buried fault scarps' or geothermal rock alteration. Magnetics are
used to define magnetic anomalies associated with the geothermal resource.
With passive seismic exploration, micro-earthquakes are monitored to
determine a seismically active area possibly associated with a fault.
Audio magnetotellurics (AMT) and magnetotellurics (MT) are used to locate
basement rock anomalies that might be associated with a geothermal
a. Tufa mound--mound formed around the mouth of a hot spring. Formed by
chemicals deposited from the spring water (ca cium carbonate o r silica).
b. Hydrothermally altered rock--rock changed i n chemical composftion by
long-time contact with hot geothermal fluid.
c.
Fault scarps.
24
I
Resistivity
-
Geochemical
soil survey
J
Relatively inexpensive,
good data
Questionable data
Figure 5.
Recommended Order o f Geophysical Surveys
25
resource. The information obtained by the above geophysical methods can,
under suitable conditions, provide the investor with additional data to aid
in the decision maki,ng process.
Geochemical investigations entail sampling any available geothermal
fluids, determining the concentrations of chemical constituents, and then
interpreting the results. The chemical constituents provide data necessary
to indicate the suitability of the expected geothermal fluid for the
intended application(s), the system design and construction, and the method
of disposal. Fluid constituents are of interest i n (a) geochemical
thermometry, (b determination of ground-water flow systems,
(c) exploration using soil gases and particulates, (d) corrosion,
(e) scaling, and (f) common environmental problems (See Table 1).
The target and conceptual model is revised to incorporate the data
obtained through the aforementioned activities to determine i f t h e project
development should be continued, halted, or investigated further.
6.7 Exploratory Well Drilling
Positive indicators obtained from the exploratory activities can
result in the drilling of an initial (exploratory) well. An initial or
wildcat well i n any particular area where a minimal data base on
ground-water temperature, well production rates and water quality exists,
will usually be regarded by state regulatory agencies as an "exploration"
well. Such terminology (a) does not inhibit well construction design or
size, (b) often facilitates disposal o f well fluids during testing, and
(c) may limit the initial test duration. Regulatory agencies, upon
obtaining data on water quality, reservoir parameters, and basic production
characteristics from the initial well, will usually approve applications
for extended testing periods and later conversion to a production well
permit if the test results merit the change. However, in the initial
drilling permit application, it may be best to use the term "exploration
well" to define the well type.
26
6.8
Reservoir Testing
The next c o n t i n u i n g element in r e s o u r c e assessment (covered i n g r e a t e r
d e t a i l i n Reference 1) i s t h a t of r e s e r v o i r t e s t i n g . I t i s i n t h i s p o r t i o n
of t h e work t h a t t h e developer d e t e r m i n e s t h e we1 and r e s o u r c e
c h a r a c t e r i s t i c s ; i . e . t e m p e r a t u r e , d i s c h a r g e r a t e v e r s u s drawdown
r e l a t i o n s h i p , and water q u a l i t y . These r e s e r v o i r parameters a r e a key t o
a s s e s s i n g t h e economics of t h e p r o j e c t i n g r e a t e r d e t a i l because t h e y w i l l
h e l p determine ( a ) i f m u l t i p l e w e l l s w i l l be r e q u i r e d , ( b ) i f f l u i d can be
disposed i n t o a s u r f a c e water body o r i f an i n j e c t i o n well w i l l be
r e q u i r e d , ( c ) i f pumping t h e production well w i l l be n e c e s s a r y , and ( d ) i f
c o r r o s i o n / s c a l i n g w i l l be major p r o j e c t c o n s t r a i n t .
Reservoir t e s t i n g r e s u l t s a r e f a c t o r e d i n t o t h e economic a n a l y s i s o f
the proposed p r o j e c t and a go, no-go d e c i s i o n i s made. P o s i t i v e r e s u l t s
w i l l g e n e r a l l y l e a d t o r e s o u r c e development a s shown i n Figure 6 .
27
1
Estimate resource
I
i
Yes
Develop resource
.
Proceed or
upgrade
application
Gest = Gact
Proceed
Downgrade
application
Gest = Estimated geothermal resource
tG
,,
= Actual geothermal resource
F i g u r e 6.
Outcomes of Resource Assessment
28
lNEL3 3991
7.
PROJECT CONSIDERATIONS AND RISKS
7.1
General
The i n v e s t o r , i n t h e c o u r s e of performing r e s o u r c e assessment,
n a t u r a l l y s e e k s t o avoid any unnecessary r i s k s .
There a r e , however,
i n h e r e n t r i s k s t o geothermal r e s o u r c e development and some of these risks
a r e discussed i n t h i s section.
Four major risk a r e a s a r e ( a ) t e c h n i c a l , ( b ) c o s t , ( c ) t h e market
p l a c e and ( d ) i n s t i t u t i o n a l . Technical risks a r i s e from t h e chances t h a t
a v a i l a b l e technology w i l l not permit performance of t h e r e q u i r e d t a s k s .
Cost r i s k s a r e r e l a t e d t o g r e a t e r than expected c o s t s t o develop t h e
r e s o u r c e , c o n s t r u c t t h e system, o r f i n a n c e the p r o j e c t . Market r i s k s
concern t h e p r i c e s of both geothermal energy and a l t e r n a t i v e energy
s u p p l i e s , and a l s o consumer a c c e p t a n c e . I n s t i t u t i o n a l r i s k s occur because
of environmental, economic, and o t h e r forms of r e g u l a t i o n t h a t geothermal
development f a c e s . In t h e r e s o u r c e assessment s t a g e , a n i n v e s t o r would most
l i k e l y f a c e t e c h n i c a l and c o s t r i s k s . However, a l l r i s k s and economics
should be r e e v a l u a t e d a s new d a t a become a v a i l a b l e t o avoid unnecessary
spending, i f a p r o j e c t should become i m p r a c t i c a l .
7.2
Resource Development C o n s i d e r a t i o n s and Risks
T h e m o s t d i r e c t r i s k s a r e caused by a d i v e r g e n c e between expected
r e s o u r c e c h a r a c t e r i s t i c s and a c t u a l c o n d i t i o n s . There a r e a number o f
f a c t o r s t h a t c o n t r i b u t e t o t h i s . Nonuniform water supply c h a r a c t e r i s t i c s
of f r a c t u r e d and u n f r a c t u r e d rock s t r u c t u r e s e x i s t . P r o l i f i c ground-water
a q u i f e r s may mask t h e deeper geothermal r e s o u r c e s , making i t d i f f i c u l t t o
p r e d i c t a t - d e p t h t e m p e r a t u r e s . Low geothermal f l u i d s production r a t e s ,
e x c e s s i v e pump-lift needs, lower than needed r e s o u r c e t e m p e r a t u r e s , and
o t h e r undesired f l u i d c h a r a c t e r i s t i c s could a f f e c t use and/or d i s p o s a l .
There a r e o t h e r risks b u t these a r e l e s s important d u r i n g t h e r e s o u r c e
development s t a g e .
For instance, the d e v e l o p e r a c c e p t s a r i s k when he
d e c i d e s t o i n i t i a l l y a s s e s s the r e s o u r c e and o b t a i n l e a s i n g r i g h t s , b u t t h e
29
magnitude of the investment is low. There is also a risk that the
assessment could indicate a poor resource when a suitable resource exists.
It is important that a phased approach to development, using qualified
technical support, be followed in order to proceed through a series of
decision points that will minimize risks to the developer. Major
investments are related to production well drilling and system design and
construction, and cost risks can be reduced by characterizing the
geothermal resource as accurately as practical. Actual project experience
stresses the economic worth of adequate geological and geophysical surveys.
The development
risk considerations,
source. Prudent and
resource development
o f geothermal resources, although faced with certain
is proving to be a reliable and cost effective energy
reasonable management practices will help reduce the
risks.
30
8. PON PROJECTS EXPERIENCE
8.1
General
Resource assessment development and considerations have been generally
discussed in the previous sections. Experience gained from the 23
DOE-funded PON projects verify much of that which has been stated, and
relative information-about these projects is provided to help tie the
discussions to specific examples.
Reviewing the experiences gained at the sites is important for two
major reasons. First, there appears to be many additional sites,
especially in the western United States, where potentially usable
geothermal resources exist. Secondly, there are lessons to be learned from
the pioneering geothermal direct-use heat resource assessment activity,
which should be applied to any future efforts to use geothermal energy
di rectly .
Fifteen of the PON projects are in operation, seven were abandoned,
and one was awarded but did not begin. Table 4 lists these projects, their
location, administering DOE field office, and status. Although certain of
the PON projects were abandoned, valuable resource assessment data were
obtained for the benefit of future developers; the projects therefore
cannot be considered failures. A private development at Kelley Hot
Springs, California was successful after the PON project was stopped when
it encountered archaeological artifacts. A good quality resource with a
peak flow rate o f 600 gpm at 165OF was found at Monroe, Utah, but the town
was not able to find an economical use for it. (It is still available for
use.) The Moana/Reno, Nevada project obtained a resource, but it required
too long a pipeline to be constructed within available funding. Injection
problems caused the El Centro, California city counci to lose interest in
their project. The Douglas, South Dakota High School project was not
pursued because a drill strjng became stuck in the we 1 prior to contract
commitment between the school and DOE.
31
TABLE 4.
GEOTHERMAL DIRECT USE PON PROJECTS
Project
Location
DOE
Office
Status
Agribusiness
Aquafarms, I n t l .
Dos Palmas Area, CA
SAN
Operating.
prawns.
Diamond R i n g Ranch
Haakon County, SD
ID
Operational. Not
i n use. Ranch f o r
s a l e , unoccupied.
K e l l e y Hot Springs
A g r i c u l t u r e Center
K e l l e y H o t S p r i n g s , CA
SAN
Discontinued.
Archaeological s i t e
interference.
U t a h Roses, I n c .
Sandy, UT
ID
Operating.
roses.
H o l l y Sugar
Brawley, CA
SAN
Discontinued.
Inadequate f l o w ,
deep r e s o u r c e .
Ore-Ida Foods
O n t a r i o , OR
ID
Discontinued.
Inadequate f l o w
deep r e s o u r c e .
B o i se
Boise, I D
ID
O p e r a t i n g : c i t y and
water d i s t r i c t
systems o p e r a t i n g .
E l Centro
E l Centro, CA
SAN
Discontinued.
M a r g i n a l , sandy
resource.
E l ko
E l k o , NV
ID
Operating.
K1amath Fa1 1 s
Klamath F a l l s , OR
SAN
O p e r a t i n g on
temporary p e r m i t
Madison County
Rexburg, I D
ID
D i s c o n t i nued.
Growing
Growing
I n d u s t r i a l Processes
D i s t r i c t Heating
Inadequate tempera t u r e resource.
32
TABLE 4.
(continued)
Loca t ion
Project
DOE
Office
Status
D i s t r i c t Heating (continued)
Moana
Reno, NV
SAN
P a r t i a l l y completed.
Suspended f o r
renegotiation.
Monroe C i t y
Monroe C i t y , UT
ID
D i s c o n t i nued.
Resource, c o s t and
m a r k e t p r o b l ems.
Pagosa S p r i n g s
Pagosa S p r i n g s , CO
ID
O p e r a t i n g on
temporary s t a t e
production permit
Susanville
Susanvi 11e , CA
SAN
Operating.
Douglas H i g h School
Box E l d e r , SD
ID
PON scope n o t
started. D r i l l i n g
f a i 1u r e .
Klamath County YMCA
Klamath F a l l s , OR
SAN
Operating.
Navarro College
Corsicanna, TX
NV
Operating.
P h i l i p School
P h i l i p , SD
ID
Operating.
S t . Mary's Hospital
P i e r r e , SD
ID
Operating w i t h
1 0 8 O F resource
T-H-S
Hospital
M a r l i n , TX
NV
Operating.
Utah S t a t e Hospital
D r a p e r , UT
ID
Operating.
Warm S p r i n g s
State Hospital
Warm S p r i n g s , MT
ID
Operating. P a r t i a l
l o a d on a r t e s i a n
flow.
Institutional
33
8.2
I n i t i a l PON P r o j e c t I n t e r e s t
I n i t i a l i n t e r e s t f o r most o f t h e PON p r o j e c t s o c c u r r e d as a r e s u l t o f
s u r f a c e m a n i f e s t a t i o n s o r t h e e x i s t e n c e o f nearby warm w a t e r w e l l s , and
T a b l e 5 l i s t s t h e p r i m a r y reason f o r t h e i n i t i a l i n t e r e s t i n each
project's.
Warm w a t e r w e l l s a l r e a d y e x i s t e d on t h e p r o p e r t y i n t h r e e
cases; i n two, warm w a t e r w e l l s were known t o e x i s t i n t h e a r e a near t h e
p o t e n t i a l geothermal p r o j e c t ; h o t s p r i n g s were l o c a t e d i n t h e immediate
r e g i o n f o r seven p r o j e c t s .
Geothermal d e v e l o p e r s had chosen s i t e s i n KGRA
i n c l u d i n g an a r e a a q u i f e r f o r s i x a p p l i c a t i o n s ; d e v e l o p e r s , i n f o u r cases,
a p p a r e n t l y began t h e p r o j e c t based on e x i s t i n g g e o l o g i c a l and g e o p h y s i c a l
r e c o r d s and surveys; and, i n t h r e e used area a q u i f e r s .
T h i s experience
demonstrates t h e s i g n i f i c a n c e o f s u r f a c e m a n i f e s t a t i o n s as a c a t a l y s t f o r
p r o j e c t development.
8.3
PON P r o j e c t Resource C h a r a c e r i s t i c s
Geothermal r e s o u r c e i n t e r e s t r e s u l t e d i n t h e e v e n t u a l development o f
22 PON p r o j e c t s .
(The 23rd p r o j e c t a t Douglas H i g h School i n Box E l d e r ,
South Dakota was stopped v e r y soon a f t e r i t s s t a r t .
The school d i s t r i c t
c o u l d n o t d e v e l o p a p r o d u c t i o n w e l l , due t o a d r i l l stem b e i n g t r a p p e d i n
t h e w e l l , w h i c h c o u l d n o t be removed o r bypassed.)
The geothermal f l u i d s
o b t a i n e d f r o m t h e w e l l s d r i l l e d f o r t h e PON p r o j e c t s were g e n e r a l l y i n t h e
e x p e c t e d t e m p e r a t u r e range w i t h adequate f l o w . T h i s . i s shown i n T a b l e 6
w h i c h summarizes t h e a v a i l a b l e r e s o u r c e c h a r a c t e r i s t i c s f o r t h e PON p r o j e c t
w e l l s . A few o f t h e w e l l s d i d n o t a c h i e v e t h e d e s i r e d c h a r a c t e r i s t i c s , b u t
v a l u a b l e i n f o r m a t i o n and e x p e r i e n c e were o b t a i n e d t o enhance t h e
t e c h n o l o g i c a l d a t a base f o r t h e geothermal i n d u s t r y . Some o f t h e l e s s o n s
l e a r n e d and p r o j e c t c h a r a c t e r i z a t i o n o b s e r v a t i o n s a r e p r o v i d e d f o r t h e
reader' s b e n e f i t .
W e l l y i e l d p r e d i c t i o n s were i n a c c u r a t e i n more cases t h a n t h o s e f o r
temperature, r e f l e c t i n g the r e l a t i v e r i s k .
Project s i t e s are often
s e l e c t e d p r i m a r i l y on e x i s t i n g o r expected r e s o u r c e t e m p e r a t u r e i n f o r m a t i o n
t h a t i s based on t e m p e r a t u r e s i n d i c a t e d by chemical geothermometers.
g e o p h y s i c a l t e c h n i q u e s , however, do n o t y i e l d d a t a t h a t can be used t o
34
The
TABLE 5.
REASONS FOR PON PROJECTS I N I T I A L INTEREST I N RESOURCE DEVELOPMENT
Reason
Project
Aqua f a rms
B o i s e City
Diamond R i n g Ranch
E l Centro
E l k 0 Heat Company
WWP
WWP/WN
H o l l y Sugar
K e l l e y Hot Springs
Klamath County YMCA
Klamath Fa1 1 s
Madison County
WN
HS/ER
KGRA/WWN
KGRA/WWN
ER/WN
Monroe City
Navarro College
Ore-Ida
Pagosa S p r i n g s
P h i 1 i p School
HS
ER
ER
HS
KGRA/AA
Reno, Moana KGRA
S t . Mary's Hospital
Susanville
T-H-S H o s p i t a l
Utah Roses
KGRA/HS/WWN
KGRA/AA
HS
WWP/AA
KGRA
HS/ER
WWN
ER
Utah State Prison
Warm S p r i n g s S t a t e H o s p i t a l
HS/WN/KGRA
HS
Key :
WWP = e x i s t i n g warm w a t e r w e l l s on p r o p e r t y
WWN = e x i s t i n g warm w a t e r w e l l s nearby
HS = h o t s p r i n g s i n t h e a r e a
KGRA = known Geothermal Resource Area ( a s d e s i g n a t e d by t h e U.S.G.S.)
ER = e x i s t i n g r e c o r d s and s u r v e y s
AA = a r e a a q u i f e r .
35
TABLE 6.
EXPECTED VS.
ACTUAL RESOURCE C H A R A C T E R I S T I C S
.D i scha r q e
(gpm)
We1 lhead
Tempera t u r e
_- Am-
Pro.iect We I I s
Aquafarms
-
Boise C i t y
F-1
F-2
F- 3
F-4
-
BWSWD 1
BWSWD 2
DWSWD 3
BGL
BGL
. BGL
DGL
--
o?
4
Flow
Outcome
79-92f
83f
107:
86
I n e x p e c t e d range
I n expected range
G r e a t e r t h a n expected
I n expected range
Adequate
Adequate
I nadequa t e
Adequate
170f
170f
134f
N/A
N/A
Lower t h a n expected
Adequate
Adequate
Inadequate
155f
172f
166f
170f
In
In
In
In
I nadequa t e
Adequate
Adequate
Adequate
expected
expected
expected
expected
range
range
range
range
Comments
Existing well
E x i s t i n g we1 I
Abandoned
Diamond R i n g Ranch
152
N/A
Adequate f
Existing well
E l Ceritro
250
N/A
Inadequate
abandoned
E l k o Heat Company
w
1
2
3
TemReratUre Outcome
-
EtIC No.
1
--
178
I n expected range
Adequate f
157
I n expected range
--
Adequate
H i g h Rad i um-226
Lower t h a n expected
lnadequatef
D r y Hole
Kel l e y Hot S p r i n g s
1lo
N/A
Klamath County YMCA
147-1331
Klamath Fa1 I s CW-1&2
21 2-2301
Iiaakon School ( P h i I P I SD)
HoI l y Sugar
Mad i son County
Monroe C i t y
Navarr'o C o l l e g e
-
Production
injection
G r e a t e r t h a n expected
N/A
-Adequate
Not d r i I l e d
Tempera t u r e decreased
Adequa t e e
-
70
Lower t h a n expected
Inadequa t e e
164
Lower t h a n expected
Inadequate
Economics
imited
124h
I n expected range
N/A
Adequa tec.d,f
I nadequa t e
Low f l o w ;
Inject ion
ow tempera t u r e
imited
--
TABLE 6.
( c o n t i nued )
D i scha rqe
Pro.iect We1 I s
We I I head
Tempe r a t u r e
(F )
--
Ore- Ida
-
(9pm)
Tempe r a t u r e Outcome
Artesian
I n expected range
With
Flow
Pump
011tcome-
--
1
I nadequa t e
D r y Hole
---
Adequate
I nadequa t e
Adeq u a t e b .e
Interference I i m i ted
P I ugged/ahandoned
Interference I i m i ted
--
600
228
1150
Comments
131
118
148
I n expected range
Lower t h a n expected
G r e a t e r t h a n expected
160h
185h
I n expected range
I n e x p e c t e d range
--
108
900
600
Adaqua t e b.
Adequate
Ma r y ' s tiosp i t a I
108
Lower than expected
375+
--
Adequate
--
-
175
G r e a t e r t h a n expected
--
750
Adequate
--
THS llosp i t a I
153
I n e x p e c t e d range
3 15
Adequate
--
U t a h Roses
123
I n expected range
--
230
Adequate c ,
--
Utah S t a t e P r i s o n
180
I n expected range
600+
288
Adequate
--
Warm S p r i n g s S t a t e H o s p i t a l
156
Lower t h a n expected
60
Adequate
Pagosa S p r i n g s
Reno;
St.
PS-3
PS-4
PS-5
Moana KGRA
Sa I em- 1
NNB- 1
Susanvi I l e
Susan 1
75
35
U
N / A = Not a v a i l a b l e
a.
G i v e n t h e temperature.
b.
G r e a t e r t h a n expected.
c.
Less t h a n expected.
d.
Adequate f o r p r o j e c t t o c o n t i n u e a t reduced scope.
e.
DOE Geothermal D i r e c t Heat A p p l i c a t i o n s Program Summary,
September 1981,
f.
DOE Geothermal D i r e c t Heat A p p l i c a t i o n s
August 1982, Op. C i t .
9.
Morrison
h.
Persona I communication w i t h p r o j e c t p e r s o n n e l b y EG&G Idaho,
-
Knudsen Company,
Inc.,
Program Summary,
Utah S t a t e P r i s o n Geothermal Test,
Inc.,
6p. C i t .
Septoniber 1982.
December 1983.
cld
C o r r o s i v e and S c a l i n g
estimate well productivity. Only production wells i n the area can be used
to provide even a crude estimate of expected well productivity.
Occasionally, development may continue by modifying the planned project
even though results are less than expected. For example, the expected
temperature and pumped flow were 171OF and 300 gpm for space and hot water
heating at the Warm Springs State Hospital. When 156OF and 60 gpm were
obtained, only water heating was used. The scope was cut to fit the
resource.
Sometimes, when resource characteristics are different than estimated,
tradeoffs can be made. For instance, a higher temperature can allow a
lower well discharge rate, because the extractable energy for a given use
is the product of the temperature change (drop) of the geothermal fluid
passing through a heat exchanger, and the flow rate. Higher than expected
temperatures and flow rates may make i t economically feasible to include
measures to remove an unexpected undesirable chemical from the fluid. If
the temperature and/or well productivity i s lower than expected, it may be
possible to reach project heat demands by one or more o f the following;
(a) increasing the geothermal fluid flow rate through the heat exchangers
by using a larger pump and motor which might be set deeper in the well
because o f more drawdown of the fluid level in the well, (b) enlarging the
heat exchangers, (c) increasing the insulation on pipelines to minimize
transmission heat losses, (d) installing a variable speed pump to minimize
well drawdown, (e) installing a second well, and (f) installing a heat
pump, at the wellhead or after initial use, to raise the temperature of the
geothermal fluid. There are many courses of action that can be taken to
mitigate the effects of low well productivity/temperature. Cost-to-benefit
ratio evaluations will help make the proper choices.
Wellhead temperatures that were unexpectedly low were due to
overestimating the resource temperature using geothermometry, such as at
Monroe, Utah, or having a prolific cold water aquifer system which prevents
heat buildup, as at the Madison County, Idaho project.
The process of site selection and exploration used at the Ore-Ida
project demonstrates the value of reviewing existing data. 11,12 The
38
s u r f a c e geology was a l r e a d y mapped i n t h e a r e a .
Subsurface geology was
i n t e r p r e t e d from e x i s t i n g o i l and gas e x p l o r a t i o n h o l e s t h a t were up t o
11,935 f t deep.
A d e t a i l e d p r i v a t e g r a v i t y survey was o b t a i n e d and was
f o u n d t o be c o m p a t i b l e w i t h p r e v i o u s p u b l i c s u r v e y s .
A magnetic anomaly
map o f t h e area was produced u s i n g d a t a o b t a i n e d f r o m Oregon S t a t e
University.
A r e f l e c t i o n s e i s m i c survey was t h e m a j o r a c t i v e work
undertaken f o r t h e p r o j e c t .
The g e o c h e m i s t r y o f t h e r m a l and nonthermal
w a t e r s f r o m w e l l s and s p r i n g s was o b t a i n e d b y a p r o j e c t survey and f r o m
a v a i l a b l e p u b l i c surveys.
However, even w i t h a l l t h e d a t a o b t a i n e d d u r i n g
e x p l o r a t i o n , t h e s i t e was n o t s a t i s f a c t o r y because t h e completed w e l l ,
w h i c h was o v e r 10,000 f t deep,13 had a l o w f l u i d y i e l d .
The e x p e r i e n c e g a i n e d t h r o u g h t h e Pagosa S p r i n g s , Colorado p r o j e c t
14
e x e m p l i f i e s some o f t h e u n c e r t a i n t i e s t h a t e x i s t i n t h e development o f a
geothermal r e s o u r c e i n a complex f r a c t u r e - f l o w dominated media.
It also
i l l u s t r a t e s t h e s i g n i f i c a n t l e v e l o f u n c e r t a i n t y a s s o c i a t e d even w i t h
r e s o u r c e s t h a t have been p r e v i o u s l y e x p l o i t e d .
I n t h i s p r o j e c t , a new w e l l
d r i l l e d o n l y 30 f t f r o m a t e s t w e l l produced geothermal f l u i d t h a t was 10°F
c o o l e r t h a n t h a t o f t h e t e s t w e l l a t comparable d e p t h .
A second w e l l
l o c a t e d 350 f t from t h e f i r s t one had such l o w t e m p e r a t u r e and f l o w t h a t i t
was abandoned.
A t h i r d new w e l l , d r i l l e d 180 f t f r o m t h e f i r s t one and
30 f t f r o m an e x i s t i n g o l d w e l l , produced a much h i g h e r t e m p e r a t u r e and
greater f l o w than e i t h e r .
The h y d r o g e o l o g i c f l o w system i n t h a t case i s
v e r y complex and heterogeneous i n r e g a r d s t o t h e w a t e r y i e l d from f r a c t u r e s
and t h e i r a s s o c i a t e d f l u i d t e m p e r a t u r e s .
The o n l y r e l i a b l e method t o
d e t e r m i n e t h e t e m p e r a t u r e and d i s c h a r g e c h a r a c t e r i s t i c s i s by means o f an
exploration o r production well.
The e x t e n s i v e i n t e r c o n n e c t i o n o f t h e w e l l s
n e c e s s i t a t e d e x t e n s i v e i n t e r f e r e n c e f l o w t e s t s as a p r e r e q u i s i t e t o
o b t a i n i n g a p r o d u c t i o n p e r m i t f o r a new w e l l .
The presence o f Radium 226 i n t h e f l u i d a t t h e P h i l i p South Dakota
p r o j e c t not only required the i n s t a l l a t i o n o f special treatment f a c i l i t i e s ,
b u t a l s o r e s u l t e d i n schedule d e l a y s and c o s t i n c r e a s e s .
A more common
problem i s c o r r o s i o n o r s c a l i n g caused by t h e geothermal f l u i d .
Well
c a s i n g c o r r o s i o n i s commonly t h e f a c t o r l i m i t i n g t h e e x p e c t e d l i f e o f a
w e l l , and s p e c i a l c o n s i d e r a t i o n i n t h e purchase o f m a t e r i a l s 2nd equipment
39
is often necessary to minimize the adverse effects of corrosion or
scaling. (Corrosion problems can be minimized by about three months of
corrosion coupon tests in piping flowing the geothermal fluid and analyzing
the test data prior to designing the system.)
A major lesson learned from the PON projects experience to date is the
importance of an accurate resource assessment. The resource assessment
stage is a relatively low cost operation, but through this effort, an
investor decides whether and where to proceed with the next step in project
implementation, which is production well drilling. Well drilling is a
major cost component of a geothermal energy supply system, and project
success or failure can depend on the quality of the resource assessment's
guidance for the drilling program. The geothermal resource characteristics
that are important to project performance include fluid wellhead
temperature, discharge rate, drawdown characteristics and fluid chemistry
(e.g., salinity, dissolved solids, radioactive elements). Some o f these
items may be determined by drilling small test wells prior to drilling the
production well. The PON project experience indicates that, although
resource assessment remains an art, where results are associated with
significant uncertainty, the resource estimate has generally proved
accurate enough to provide a basis for investment decisions. Reference 1
provides additional experiential information about the PON projects.
8.4 Cost Information
Cost information, specifically for the resource assessment part of the
PON projects, is not readily available, and varied considerably from
project to project. Some of the projects required very little additional
resource assessment work due to the availability of existing geological
data. Where exploration is a small part o f the total project, costs were
not separately identified. Information is provided for three of the PON
projects to give an overall idea of resource assessments costs.
The Philip, South Dakota school project is located over an easily
sited area aquifer (the Madison); however, little detailed, local data
existed. About $3000 was spent in 1978 on geological and geophysical
40
surveys.
B o r e h o l e g e o p h y s i c a l l o g g i n g i n 1979 c o s t about $8400 a f t e r
d r i l l i n g , $1300 was spent on f l o w t e s t i n g equipment.
The Klamath F a l l s ,
Oregon YMCA p r o j e c t u t i l i z e d a w e l l d e f i n e d , f a u l t dominated r e s o u r c e .
Several l o c a l geothermal u s e r s a l r e a d y e x i s t e d i n t h e a r e a .
The c o s t
e s t i m a t e f o r t h i s p r o j e c t i d e n t i f i e s o n l y one r e s o u r c e assessment a c t i v i t y ,
well testing after d r i l l i n g .
The c o s t was a p p r o x i m a t e l y $3500 i n 1978.
The Ore-Ida Foods p r o j e c t a t O n t a r i o , Oregon, a t t h e o t h e r extreme,
was f o r a l a r g e i n d u s t r i a l a p p l i c a t i o n i n an area t h a t had v e r y p o o r l y
d e f i n e d i n d i c a t i o n s o f a resource.
P r i o r t o d r i l l i n g , about $10,000 was
spent g a t h e r i n g and assessing a v a i l a b l e d a t a .
I n a d d i t i o n , an a c t i v e
s e i s m i c survey, u s i n g small dynamite charges, c o s t o v e r $112,000.
However,
t h i s e x p e n d i t u r e i s small i n p r o p o r t i o n t o t h e p r o d u c t i o n w e l l c o s t o f
$2.3 m i l l i o n , w h i c h i n c l u d e d $180,000 i n w e l l t e s t i n g .
A d d i t i o n a l p r o s p e c t c o s t i n f o r m a t i o n i s p r o v i d e d i n I C F ' s r e p o r t "An
15
Economic Assessment o f Nine Geothermal D i r e c t - U s e A p p l i c a t i o n s " .
41
9.
CONCLUSIONS AND RECOMMENDATIONS
9.1
Conclusions
The most s i g n i f i c a n t c o n c l u s i o n s d e r i v e d f r o m t h e PON p r o j e c t s f o l l o w .
1. About 75% o f t h e PON p r o j e c t s s t a r t e d a r e c u r r e n t l y o p e r a t i n g and
are t e c h n i c a l l y successful.
2.
Most o f t h e u n s u c c e s s f u l p r o j e c t s were stopped because an adequate
r e s o u r c e was n o t o b t a i n e d f r o m t h e f i r s t p r o d u c t i o n w e l l d r i l l e d by t h e
project.
3.
The i n i t i a l i n t e r e s t i n most o f t h e p r o j e c t s was t h e r e s u l t o f
nearby h o t s p r i n g s or warm-water w e l l s .
4.
The d e s i g n o f t h e geothermal systems i s w i t h i n t h e
state-of-the-art
i f c o r r o s i o n coupon t e s t s a r e made w i t h t h e s u b j e c t
geothermal p r o d u c t i o n w e l l .
5. Small compromises i n t h e d e s i g n o f t h e u s e r s system can o f t e n
o f f e r t h e f l e x i b i l i t y t o accommodate d e v i a t i o n s f r o m t h e o r i g i n a l e s t i m a t e
o f t h e resource c h a r a c t e r i s t i c s .
T h i s can r e s u l t i n s u c c e s s f u l p r o j e c t s
w h i c h m i g h t o t h e r w i s e be dropped.
6.
Making use o f a v a i l a b l e r e s o u r c e d a t a and a s t r u c t u r e d d e c i s i o n
p r o c e s s can m i n i m i z e t h e c o s t and number o f u n s u c c e s s f u l w e l l s and p r o j e c t s .
7. A p p l i c a t i o n s w h i c h r e q u i r e a c o n t i n u o u s , f i x e d h e a t i n p u t have
b e t t e r economics t h a n space h e a t i n g o r d i s t r i c t h e a t i n g a p p l i c a t i o n s w h i c h
a r e seasonal and o n l y use a b o u t 20 t o 30% a v a i l a b l e annual c a p a c i t y of t h e
geothermal systems.
42
9.2
Recommendations
The f o l l o w i n g recommendations a r e made t o i n v e s t o r s and d e v e l o p e r s o f
d i r e c t - u s e geothermal systems.
1.
Match expected r e s o u r c e c h a r a c t e r i s t i c s w i t h t h e r e q u i r e m e n t s o f
p r o s p e c t i v e uses and r e v i e w economics.
2.
Update t h e resource/use match and economics whenever new r e s o u r c e
d a t a becomes a v a i l a b l e .
3.
I n i t i a l l y , assume t h a t i n j e c t i o n o f t h e spent geothermal i s
r e q u i r e d f o r a c o n s e r v a t i v e economic e v a l u a t i o n , b u t a t t e m p t t o f i n d
r e s o u r c e s w h i c h meet s u r f a c e d i s p o s a l r e q u i r e m e n t s .
Surface disposal w i l l
s i g n i f i c a n t l y improve p r o j e c t economics.
4.
Make f u l l use of a v a i l a b l e g e o l o g i c a l and g e o p h y s i c a l d a t a f r o m
u n i v e r s i t i e s and p u b l i c agencies.
5.
I n v e s t i g a t e and f u l l y u n d e r s t a n d p e r m i t t i n g r e q u i r e m e n t s and l e a d
t i m e s f o r o r i g i n a l p e r m i t s and f o r m o d i f i c a t i o n s .
6.
H i r e e x p e r i e n c e d c o n s u l t a n t ( s ) f o r r e s o u r c e assessment p r i o r t o
initial drilling.
S i t i n g t h e i n i t i a l e x p l o r a t i o n / p r o d u c t i o n w e l l i s one o f
t h e most s i g n i f i c a n t p r o j e c t d e c i s i o n p o i n t s s i n c e d r i l l i n g i s t h e f i r s t
m a j o r f i n a n c i a l commitment.
43
10. REFERENCES
1.
ICF, Inc., and EG&G Idaho, inc., Resource Development, System Design,
Construction and Operation for Geothermal Direct-Use Applications,
Report No. DOE/ET/12099-4, Contract No. DE-AC07-80ID12099 and
DE-AC07-76ID01570, April 1984.
2.
ICF, Incorporated, ICF Oil and Gas Service, November, 1981.
3.
U.S.G.S, Assessment of Geothermal Resources of the United States,
1978, USGS Circular No. 790, Reston, Virginia, February 1979.
4.
Justus, Debra, et al., Oregon: A Guide to Geothermal Energy
Developement, U.S. Department of Energy, June 1980, p. 45.
5.
Interagency Geothermal Coordinating Council, Geothermal Energy
Research and Development Program, Fourth Annual Report, June 1980.
6.
Geothermal Resources Council, Special Report Number 7, Direct
Utilization of Geothermal Energy: A Technical Handbook, 1979, pp 1-6
to 1-10.
7.
Goldman, D. after Dhillon et al., 1978 draft PhD. dissertation,
University of Idaho, 1981.
8.
Douglas M. Sacarto, State Policies for Geothermal Development,
National Conference of State Legislatures, Denver, Colcrado.
9.
Op. cit.
10. Goldman, D. after Dhillon et al., 1978 draft PhD. dissertation,
University of Idaho, 1981.
11.
Ore-Ida Foods Inc., Food Processing Industry Geothermal Energy, A
field Experiment, Vol. 1, Technical Proposal, November 1977, Report
NO. DOE PON EG-77-N-03-1553.
12.
Geothermex Inc., Data Analysis and Drilling Site Selection for
Ore-Ida Property, Ontario, Oregon, October 1978, Report
DOE/ET/28424-2.
13. DOE, Geothermal Direct Heat Applications Program Summary,
September 1981, pp. 32-34.
14. DOE, Geothermal Direct Heat Applications Program Summary,
September 1981, p. 129.
15. ICF, Incorporated, An Economic Assessment o f Nine Geothermal
Direct-Use Applications,Report No. DOE/ET/12099-5, Contract No.
DE-AC07-80ID12099, December 1983.
44
APPENDIX A
OVERVIEW OF GEOTHERMAL RESOURCE TYPES
CONTENTS
1.
.....................................................
2 . TYPES OF GEOTHERMAL RESOURCES ....................................
3 . CURRENT GEOTHERMAL RESOURCE ASSESSMENT ...........................
4.
KGRA D E F I N I T I O N ..................................................
5.
PON PROJECT EXPERIENCE ...........................................
REFERENCES ............................................................
INTRODUCTION
FIGURES
A-1
A-2
A-4
A-7
A-8
A-9
APPENDIX A
OVERVIEW OF GEOTHERMAL RESOURCE TYPES
1.
INTRODUCTION
C o n s i d e r a b l e h e a t i s s t o r e d and g e n e r a t e d w i t h i n t h e e a r t h .
This heat
r e s u l t s f r o m n a t u r a l r a d i o a c t i v e decay and f r i c t i o n as w e l l a s p o s s i b l e
r e s i d u a l heat from t h e time o f t h e formation o f t h e earth.
Heat f r o m t h e
e a r t h ' s i n t e r i o r i s l o s t through a r e l a t i v e l y t h i n c r u s t which i s
a p p r o x i m a t e l y 30 km (19 m i l e s ) t h i c k i n c o n t i n e n t a l landmass a r e a .
d e v e l o p a b l e geothermal r e s e r v o i r can r e s u l t :
A
( a ) where s t e e p l y d i p p i n g
permeable f a u l t s e x t e n d i n t o a h i g h t e m p e r a t u r e p o r t i o n o f t h e e a r t h ,
(b) where near h o r i z o n t a l permeable zones o c c u r i n a h i g h t e m p e r a t u r e
p o r t i o n o f t h e e a r t h , and ( c ) as a c o m b i n a t i o n o f t h e two. S u r f a c e
a
f e a t u r e s such as t u f a mounds, h o t s p r i n g s , geysers, f u m a r o l es, h o t
w e l l s , and hydrothermal l y a1 t e r e d r o c k C may r e s u l t .
Basically, hot rock
can be f o u n d everywhere ( i f a w e l l i s d r i l l e d deep enough).
However, a
r e s o u r c e can o n l y be e x p l o i t e d where a h i g h t e m p e r a t u r e f l u i d o f s u i t a b l e
chemical c o m p o s i t i o n e x i s t s i n a h i g h y i e l d i n g zone a t an e c o n o m i c a l l y
shallow depth.
a. T u f a mound--mound around mouth o f a h o t s p r i n g . Formed by c h e m i c a l s
deposited from t h e spring water (calcium carbonate o r s i l i c a ) .
b. Fumarole--hole, v e n t , s p r i n g o r geyser w h i c h e m i t s c o n s i d e r a b l e
q u a n t i t i e s o f gases, vapor o r steam.
c . H y d r o t h e r m a l l y a l t e r e d r o c k - - r o c k changed i n chemical c o m p o s i t i o n by
l o n g - t i m e c o n t a c t w i t h h o t geothermal f l u i d .
A- 1
2. TYPES OF GEOTHERMAL RESOURCES
The geothermal areas which should be considered first for exploration
and resource development, for direct-use applications, are those where the
highest temperatures are found at shallow depths (less than 1500 ft). The
geologic phenomena contributing ta the high energy potential of geothermal
resources will not be explained in more detail in this report, but the
interested reader may find a detailed discussion in "Direct Utilization of
Geothermal Energy: A Technical Handbook". 1
One system for classifying geothermal resources follows:2
1.
Hydrothermal convectiona systems related to young igneous
intrusionsb/volcanics
2.
Faul t-control 1 ed
3.
Deep regional aquifers
4.
Geopressured reservoirs
5.
Hot dry rock.
systems
The heat associated with young igneous intrusions and/or volcanic
activity may be retained i n the rock for many thousands of years.
Fracturing or faulting of this rock may permit the development of a shallow
hydrothermal convection system. In this system, naturally-occurring ground
water circulates through the rock along faults, absorbing thermal energy.
At another location it returns to or near to the earth's surface at a much
higher temperature.
a.
Hydrothermal convection--water which is hot and flowing.
b.
Igneous intrusions--a body of molten rock which pushed (intruded) into
a body of older rock and then solidified.
A-2
In deep fault-controlled systems, thermal energy is obtained by the
deep circulation of fluid along faults or stratigraphic beds. This
circulation permits fluid to extract heat from a large volume of rock. The
temperature attained by the circulating ground water depends on the depth
to which a fault allows the water to circulate, the magnitude o f the
regional heat flow, the residence time of the water, and the amount o f
mixing with colder ground waters as it returns to the surface.
Another type o f geothermal resource is found i n deep regional (large
area) aquifers, such as the Madison Aquifer, mainly in Montana, Wyoming,
and the Dakotas. This type o f aquifer is sufficiently deep and permeable
that the water it contains is warmed by the normal heat flow of the earth.
These aquifers are rare but have the advantage of relatively low risk in
siting the geothermal well to produce from the resource since they cover
large areas.
The Gulf Coast area is characterized by geopressured resources, which
are localized occurrences where hot water i s confined in deep sedimentary
strata where the pressure exceeds that of a column of water to that depth
(hydrostatic head) and may approach the pressure of the overlying rocks
(lithostatic head). These resources are in very limited use for combined
geothermal energy and methane production, as the technology is unperfected
and exploitation is costly with depths on the order of 15,000 ft.
unexploited, at present, are hot dry rock systems. Hot dry rock
systems can be developed within a large volume o f hot rock with low natural
permeability. The permeability i s artificially induced by
hydraulic/thermal fracturing. Cool water is injected down one well, heated
in the fractured volume and returned to the surface via a second well.
This type of resource system is still in experimental development and has
not been economically demonstrated in direct heat applications of
geothermal energy.
Also
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3. CURRENT GEOTHERMAL RESOURCE ASSESSMENT
Of the different systems of geothermal resources, the hydrothermal
convection and the fault-controlled systems are the most commonly exploited
for direct heat use at this time. A general assessment o f U . S . geothermal
resources by type was performed by the U.S.G.S.3 i n 1975 and was updated
i n 1978. Another assessment, di rected towards 1 ow-temperature
resources, was issued by the USGS i n 1983. These studies indicate that hot
water-dominated hydrothermal systems are considerably more common than
vapor-dominated systems e.g. steam systems such as the oysters i n Northern
California.
Virtually all of the major hydrothermal systems identified i n the U.S.
are located i n the western third of the country. The map on the following
page (Figure l), reprinted from an Interagency Geothermal Coordinating
Council report,6 indicates the locations o f potential hydrothermal
resources. Potential low and moderate temperature geothermal waters
[<194OF (<90°C,) and 194 to 3 0 2 O F (90 to 15OOC) respectively],
identified on the map, are widely scattered through the U.S., but are still
located predominantly i n the western U.S.
Very little of the identified geothermal resource base is currently
being exploited. From identified hydrothermal convection systems
(excluding those found i n and near national parks), the amount of
potentially available heat energy at the wellhead is estimated to be
~ figure over estimates the amount of beneficial
375 xlOZ4 B ~ u .This
heat that could be provided because the development of many reservoirs may
not be economically feasible due to excessive resource depths, and piping
costs and transmission line heat losses from remote locations. On the
other hand, the estimate understates the potential geothermal resource base
by excluding undiscovered hydrothermal systems, as well as all other types
of deposits, such as hot dry rock or geopressured resources.
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e'
For a resource t h a t must be used close t o i t s source, attractiveness
depends n o t only upon the nature of the resource, b u t also on the energy
demand in the surrounding area. The incentive t o exploit the geothermal
resource i s greater i n regions of the U . S . where the price of fossil fuels
i s very h i g h .
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4.
KGRA DEFINITION
The U.S. G e o l o g i c a l Survey (USGS) has d e s i g n a t e d c e r t a i n l a n d s as
A KGRA i s d e f i n e d as h a v i n g
8
9
geothermal energy e q u i v a l e n t t o 8.18 x 10 B t u ( a b o u t 1.5 x 10
Known Geothermal Resource Areas (KGRAs).
barrels-of-oil
equivalent).
I n t h e Federal "Geothermal Steam A c t o f 1970,"
a KRGA i s l e g a l l y d e f i n e d a s "an a r e a i n w h i c h t h e geology, nearby
d i s c o v e r i e s , c o m p e t i t i v e i n t e r e s t s , o r o t h e r i n d i c e s would, i n t h e o p i n i o n
o f t h e S e c r e t a r y , engender a b e l i e f i n men who a r e e x p e r i e n c e d i n t h e
s u b j e c t m a t t e r t h a t t h e p r o s p e c t s f o r e x t r a c t i o n o f geothermal steam o r
a s s o c i a t e d geothermal r e s o u r c e s a r e good enough t o w a r r a n t e x p e n d i t u r e s o f
money f o r t h a t purpose . I '
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5. PON FROJECT EXPERIENCE
O f t h e t y p e s o f geothermal r e s o u r c e s p r e v i o u s l y d e s c r i b e d , none o f t h e
PON d i r e c t h e a t a p p l i c a t i o n s e x p l o i t e d geopressured r e s e r v o i r s o r h o t dry
rock.
However, t h e o t h e r t h r e e t y p e s o f systems were e x p l o t e d i n t h e PON
p r o j e c t s , e i t h e r s i n g u l a r l y o r i n combination.
a q u i f e r o f l a r g e s t a e r i a l e x t e n t i n t h e U.S.
F o r example
t h e geothermal
i s t h e Madison A q u i f e r , w h i c h
e x t e n d s under t h e w e s t e r n h a l f o f South Dakota and i n t o t h e b o r d e r i n g
s t a t e s o f Wyoming, Montana, and N o r t h Dakota.
O f t h e 23 PON p r o j e c t s
r e f e r e n c e d i n t h i s r e p o r t , t h r e e o b t a i n t h e i r geothermal r e s o u r c e f r o m t h i s
aquifer:
Diamond R i n g Ranch, P h i l i p School, and S t . M a r y ' s H o s p i t a l , a l l
i n South Dakota.
A l l the o t h e r PON p r o j e c t s were l o c a t e d i n
f a u l t - c o n t r o l l e d systems.
( I t i s necessary f o r t h e w e l l t o p e n e t r a t e a
f a u l t i n a f a u l t - c o n t r o l l e d system i n o r d e r t o o b t a i n a f l o w r a t e
s u f f i c i e n t f o r an e c o n o m i c a l l y v i a b l e p r o j e c t . )
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REFERENCES
1.
Geothermal Resources C o u n c i l , S p e c i a l Report No. 7, D i r e c t U t i l i z a t i o n
o f Geothermal Energy: A T e c h n i c a l Handbook, 1979 pp 1-6 t o 1-10.
2.
Op c i t . pp 1-6 t o 1-10.
3.
USGS, Assessment o f Geothermal Resources o f t h e U n i t e d S t a t e s , 1978,
USGS C i r c u l a r No. 726 Reston, V i r g i n i a , 1975
4.
USGS, Assessment of Geothermal Resources o f t h e U n i t e d S t a t e s , 1978
USGS C i r c u l a r No. 790, Reston, V i r g i n i a , February 1979.
5.
USGS, Assessment o f Low-Temperature Geothermal Resources o f t h e
U n i t e d States,1982, USGS C i r c u l a r No. 892, Reston, V i r g i n i a , 1983.
6.
I n t e r a g e n c y Geothermal C o o r d i n a t i n g C o u n c i l , Geothermal Energy
Research and Development Program, F o u r t h Annual Report, June, 1980.
7.
USGS C i r c u l a r 790, op, c i t . p. 41.
8.
Op. c i t .
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